In communications systems, there may be a challenge to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the communications system is deployed.
For example, the introduction of digital beamforming antenna systems in access nodes, such as radio base stations, etc., could allow multiple simultaneous narrow beams to be used to provide network access to, and thus serve, multiple simultaneous terminal devices, such as user equipment (UE), etc. However, the current split in the access nodes between a radio equipment controller (REC) and a radio equipment (RE) as interconnected by the Common Public Radio Interface (CPRI) may no longer be feasible as passing the data for each individual radio chain over the CPRI interface could drive prohibitively high data rates.
In more detail, the bit rate of the current CPRI interface scales directly to the number of independent radio chains in the RE. When having e.g., a 200 MHz carrier bandwidth and 128 physical antenna elements in the beamforming antenna system, a bit rate of 530 Gbps would be needed for the CPRI interface with currently used sample rate and sample bit width. A further potential drawback with CPRI is the extra latency from uplink (UL; from terminal device to access node) sampling to the time the data can be used in downlink (DL; from access node to terminal device), as any information based on sampled data needs to be looped back from REC if to be used in RE.
One way to address the above-mentioned issues is to collapse the CPRI based architecture by removing the CPRI interface and putting the functionality of the REC in the RE. This approach has at least two drawbacks. Firstly, due to faster technological development of the REC compared to the RE, the technical lifetime of the REC is assumed to be shorter than that of the RE. Replacing the RE is more costly than replacing the REC. From this aspect it could thus be beneficial to keep the functionality of the RE as simple as possible. Secondly, the REC could be configured to make decisions spanning over multiple REs in order to make coordinated multi-sector decisions, e.g. when some REs represent coverage regions of the access node within the coverage regions of other REs (e.g. a so-called micro cell within a so-called macro cell). A collapsed architecture loses this overarching coordination possibility.
Hence, there is a need for an improved communication between the REC and the RE.